OK, let's do this. We've got 5800 and 42 and we're adding them all together.

Step 1: We'll start by adding the digits 0 & 2 in column 1 and get 2.

Step 2: We'll start by adding the digits 0 & 4 in column 2 and get 4.

Step 3: We'll start by adding the digits 8 & 0 in column 3 and get 8.

Step 4: We'll start by adding the digits 5 & 0 in column 4 and get 5.

So, 5800 + 42 = 5842.

